Concepts

 A sword that will grant great power to one who is worthy. In actuality, it's a myth that's been compounded with decades of confirmation bias. If someone succeeds and performs an amazing feat with the sword, they were worthy of the sword. If someone dies while wielding the sword, the person was not, in fact, worthy and the people had thought wrong.

 A hero who has a child but refuses to teach the child how to fight. After a couple years, when the child is finally grown up, the hero admits why they refuse to teach the child. "As a hero, it is my job to defeat the bad guys so that this place is safe for people like you to grow up and live in. If I teach you how to fight, it's like I'm admitting that no matter how much good I do, how many bad guys I defeat, it'll never be enough to make this place safe for you."

 A loner archetype mercenary/monster hunter/assassin/etc., Actually works better in a team setting and is willing to work in teams, but still acts as an add-on rather than part of the team. Actively pushes others away but deep down is very lonely ~~ mysterious past that no one knows ~~  Turns out it's because he/she have powerful enemies and knew they'd catch him/her one day, and didn't want anyone to miss or try to avenge/save him/her.